1. Field of the Invention
The present invention relates to an electromagnetically driven type injection valve (injector) which controls a fuel supplied to an engine on the basis of an electric signal transmitted from an electronic control unit so as to inject to an intake pipe.
2. Description of Related Art
An electromagnetically driven type fuel injection valve controlled so as to be opened and closed on the basis of an electric signal output from an electronic control unit is described, for example, in Japanese Unexamined Utility Model Publication No. 55-180066, and is generally used as a normally closed type structured such that the valve is opened by exciting a stopper core 6 serving as a stationary iron by applying an electric current to an electromagnetic coil 5 to attract a plunger 10 serving as a movable iron core to move backward a needle 7 having a valve structure on a leading end side, and the valve is closed by returning the plunger 10 on the basis of an urging force of a valve closing spring 111 by stopping the current application, as shown in FIG. 3.
In the electromagnetically driven type fuel injection valve 11 using the valve closing spring 111 as mentioned above, in addition to a matter that the valve body is subtly reacted to the electric signal, it is desirable that an accurate valve function is achieved over a long period.
In this case, in the valve employing the electromagnetic coil spring for the valve closing spring 111 such as the fuel injection valve 11 shown in FIGS. 3 and 4, the valve opening and closing motion is achieved on the basis of a comparative simple structure, however, in the light of securing an accuracy of the valve function, a valve employing a disc-shaped leaf spring for the valve closing spring is excellent, such as a fuel injection valve described, for example, in Japanese Unexamined Patent Publication No. 9-79107 and Japanese Unexamined Patent Publication No. 2004-211563.
In other words, since it is possible to avoid a problem that an outer peripheral portion of a valve closing spring is brought into contact with and interfered with a peripheral member in addition that a movable core and a valve body reciprocate in a floating state without any slidable portion, by employing the disc-shaped lead spring arranged perpendicularly to the reciprocating motion of the movable core, it is possible to limit the reduction of the accuracy of the valve function caused by a motion inhibition of the movable core and an abrasion of the member to the minimum.
However, in the fuel injection valve using the disc-shaped leaf spring, in addition that a predetermined magnitude (diameter) is necessary in the leaf spring for securing a predetermined valve stroke, whereby a certain level of outer diameter (horizontal width) of the fuel injection valve is necessary, the structure becomes slightly complicated and a cost increase tends to be generated. Accordingly, in addition to the technique using the disc-shaped leaf spring, there has been desired a development of a technique which can easily achieve an accuracy of the valve function over a long period even in the valve employing the electromagnetic coil spring.